OFDM Baseband Receiver Design for Wireless Communications

9

Circuit Techniques

Many types of signal-processing circuits with diverse functionalities are needed in an OFDM baseband receiver IC. Low power and low complexity are the major concerns in the design of these circuits.

9.1 Introduction

Portable wireless communication devices have experienced explosive growth recently. Consumers now demand longer and longer battery operation time in those portable devices. As a result, low-power and low-complexity circuit design for wireless communication transceivers has become crucial. In most orthogonal frequency-division multiplexing (OFDM) systems, several functional units are indispensable and play an essential role. They include fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) modules, delay lines (buffers), polar/rectangular coordinate conversion functions, numerical controlled oscillators (NCO), etc.

In OFDM systems, FFT and IFFT modules transform signals between the time domain and the frequency domain and occupy a large portion of the circuit area as well as the power consumption. Delay lines (buffers) also contribute a significant portion of area and power in the OFDM baseband receiver. Usually, they come in different memory depths and are used for data scheduling and temporary storage. OFDM synchronization often relies on the phase or magnitude of received complex signals; thus, arctangent and magnitude functions, which convert data from rectangular coordinates to polar coordinates, are also commonly seen in ...